Ringer



Oct. 19, 1954 L. A. CLEAVELAND 2,692,380

RINGER Filed March 18, 1953 INVENTOR uwwzt ym w/aazw ATTORNEYS Patented Oct. 19, 1954 RINGER Leroy A. Cleaveland, Mountainside, N. J assignor to United States Instrument Corporation, Summit, N. J., a corporation of New Jersey Application March 18, 1953, Serial No. 343,168

Claims.

This invention relates to apparatus for use in-telephone systems, and more particularly-to a frequency selective ringer for'use on party lines.

The principal object of a frequency selective ringer is to provide a means of calling, independently, any one of a number of parties on a single telephone circuit without alerting any of the unwanted parties on the same circuit. Common practice is to use five frequencies such as 16 25, 33 50, 66% cycles or 20, 30, 40, 50, 60 cycles. Five ringers each tuned to one frequency in the series may be connected between each side of the'line and ground. In this manner any one of ten'parties may be called by choosing the proper frequency and applying the current to one 'sideof the line and'ground or the other side of the line and ground, or a full metallic-line may be used; For a service of this type the ringer must have the following characteristics:

l. High degree of selectivity, must ring on one specified frequency with little tendency to ring on any other frequencies a few cycles removed from thespecified frequency, or harmonics of that frequency.

2. High degree of sensitivity, must ring on its specified frequency with a minimum of electrical power required.

3. High degree of frequency stability, must remain tuned to its specified frequency under all conditions which may be encountered in service.

Frequency selective ringers of the aforesaid general type have been known and used heretofore, the present invention residing in an improvement inxthe means for tuning a particular ringer to a selected frequency whereby such tuning may be performed more quickly and easily than in the past and whereby, likewise, a better and more compact unit is achieved than in the case of known ringers of this type, the ringer of the present invention also having better frequency stability and improved sensitivity over known ringers.

It is an object of the invention to provide a frequency selective ringer comprising the usual frame or base carrying a pair of adjustable gongs, an electromagnet connected in the ringing circuit, a permanent polarizing magnet, a pole-piece extending past one pole of the permanent magnet and both poles of the electromagnet and terminating in spaced, opposed pole tips, an armature movably supported adjacent the other pole of the permanent magnet andextending between the aforesaid *poletips, a clapper rod secured on the armature and carrying a clapper for alternately striking the gongs, and inertia means secured on the armature and extending generally parallel to the clapper rod, the clapper, clapper rod, armature, armature mounting spring, and inertia means constituting a tuned system for determining the frequency of energization of the electromagnet to which the ringer shall respond.

Attempts have heretofore been made to provide frequency selective ringers which may be tuned to various frequencies, one such device including a weight adjustably mounted on the clapper rod; This weight adds mass to the clap! per rod and adversely affects the gong .performance because of the damping effect of the weight when used as clapper, or carried on the clapper rod, and also because of the effect of the gong reaction upon the natural rate of the ringer. The gong reaction introduces confliCtingvibra-J tion characteristics, which are minimized according to the present invention by providing a second rod or beam parallel to the clapper rod, and a weight adjustable along said second rod. Neither the second rod nor the weight ever touchthe gongs or add mass to the clapper rod, which latter is relatively light and flexible. The gong reaction, therefore, is not increased by the'provision of the tuning means, and is not varied in any way by adjustment of the tuning means to accommodate different frequencies.

Accordingly it is a further objectof the invention to provide a harmonic ringer of the type in question, in which the, clapper system comprising the armature, clapper rod and clapper, and a separate rod secured to the armature and extending generally parallel to the clapper rod, and a weight secured thereon, may be readily adjusted by sliding the weight along the rod.

Other'and further objects, features and advantages will be apparent from the description which follows, read in connection with the accompanying drawings in which Figure 1 is an elevational view of a ringer constructed according to the invention;

Figure 2 is a sectional view on line 22 of Figure l;

Figure 3 is a horizontal section on line 3--3 of Figure 1: and

Figure 4. is a detailed view in perspective of the armature, clapper rod and clapper, and associated inertia means.

In order to facilitate an understanding of'the invention, reference is made to the embodiment thereof shown in the accompanying drawings The frame In is of non-magnetic material'such as aluminum or brass. The pole-piece l 5 of magnetic material extends entirely around the electromagnet [3, as seen in Figure l, and is supported in close engagement with one end or pole of the permanent magnet M and with both ends of the iron core I6 of the electromagnet. The pole-piece I5 terminates in pole tips I! and 18 which extend in overlapping relation and are spaced sufficiently apart'to admit the armature l9 therebetween. The armature I9 is supported from the frame In by means of a leaf-spring 2B and is thus free to vibrate between the pole tips [1 and [8 when the electromagnet I3 is energized by an alternating current of suitable frequency. It will be understood that the armature I9 is in close proximity to the opposite pole of the permanent magnet M to that which is in contact with the pole-piece l5 and thus would normally be attracted to one or another of the pole tips I! or [8, but is normally maintained in the position illustrated by reason of the stiffness of the spring 20. However, when an alternating current is applied across the leads 2| and 22 of the electromagnet l3, the polarity of the pole tips is alternated at the selected frequency and the armature I9 is accordingly attracted first toward one and then the other of said pole tips.

As best seen in Figure 4, the armature 19 carries a clapper rod 23 permanently secured thereto in any suitable fashion, a clapper 24 being likewise secured in any suitable fashion, as by soldering, adjacent the upper end of the rod 23. The armature also carries a second rod 25 of considerably heavier and more rigid nature than the clapper rod 23, but extending generally parallel to the latter, a weight 26 being slidably adjustable along the rod 25 to vary the inertia of the system comprising the elements l9 and 23 to 26, inclusive. The weight 26 may be secured in adjusted position on the rod 25, by means of a set screw 21.

It is usual to provide a condenser (not shown) in association with each ringer, interposed between one of the leads 2!, 22 and the main ringing circuit.

The harmonic ringer of the present invention possesses the following advantages over those heretofore used.

The ringer described herein has an unusually high degree of selectivity because of two parallel tuned systems loosely coupled to one another, the armature l9, spring 20, rod 25 and weight 27 as one system and the clapper 24 and clapper rod 23 as the other system. The combination results in one sharply tuned system which is unresponsive to other frequencies in the series and harmonics of its fundamental frequency. In previous ringers the weight functions as both inertia means and gong clapper, or, if the weight were on the clapper rod but did not itself serve as clapper, it increased the mass of the clapper rod-clapper combination, with adverse results, but did not provide a separate inertia means as in the present case. With that arrangement thetuned system must be tuned to resonance with a specified frequency when it is striking the gongs or when it is not. It cannot be in resonance in both conditions because of the detuning effect the gongs have on the system when they are struck by the clapper. If the system is tuned to resonance when striking the gongs it is off resonance before the gongs are contacted, hence a much greater amount of exciting power is required to bring the amplitude of vibration up to the point where the gongs are struck than would be the case if the system were tuned to resonance without the gong reactance. On the other hand, if the system is tuned to resonance without the gong reactance, as soon as the amplitude of vibration is great enough for the clapper to strike the gongs this added reactance immediately throws the system out of resonance with the energizing frequency and greater electrical power is required to develop the mechanical power necessary for satisfactory ringing.

With the ordinary type ringer any wear on the clapper or gongs would also have the effect of increasing the gong spacing, further affecting the response frequency.

The ringer of the present invention maintains its resonant frequency whether striking the gongs or not. Furthermore, adjustment of the gongs, spacing and dampening, will not aiTect the resonant frequency of the new ringer while it would have serious effects on the ordinary type. Spacing of the gongs is a critical adjustment on the ordinary type of fixed frequency ringer, but may be accomplished with ease on the new design because the adjustment will not seriously affect the resonant frequency. Thus the new design may be said to have a high degree of frequency stability.

The weight 26 being readily adjustable along the rod 25, the ringer may easily and quickly be tuned to the desired frequency, without regard to the spacing of the gongs. In the known ringers the spacing of the gongs has been very critical, because it affected the response frequency. The rod 25 extending generally parallel to the clapper rod 23 makes for a compact unit while, at the same time, the effective mass of the clapper 24 is not increased, since the clapper rod 23 is relatively light and flexible, and no weight is added to this rod. Impact of the clapper upon the gongs, therefore, will not injure or deform the latter, and gong reaction effects are not altered or increased by reason of the presence of the inertia means, or by changing the adjustment of the inertia means. The tone of the ringing signal, therefore, is not deleteriously afiected. Lastly, the construction is simple, rugged, and inexpensive.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In a frequency selective ringer, a frame, a pair of gongs, an electromagnet, a permanent magnet and a pole-piece mounted on said frame, said pole-piece extending from one pole of said permanent magnet past both poles of said electromagnet and terminating in spaced,'opposed pole-tips an armature movably supported on said frame adjacent the other pole of said permanent magnet and normally positioned between and spaced from said pole-tips, a clapper rod secured on said armature and carrying a clapper normally positioned between and spaced from said gongs, and separate inertia means rigidly secured on said armature, said clapper, clapper rod, armature, and inertia means constituting a tuned system for determining the frequency of energization of said electromagnet to which said armature shall respond.

2. The device according to claim 1, said inertia means comprising a beam and a weight adjustably mounted on said rigid beam.

3. The device according to claim 1, said inertia means comprising a rigid beam and a weight adjustably mounted on said beam, said beam extending generally parallel to said clapper rod and said weight being mounted for sliding adjustment therealong.

4. The device according to claim 1, said inertia means comprising a beam and a weight adjustably mounted on said beam, said clapper rod being relatively flexible and said beam being relatively rigid.

5. The device according to claim 1, said armature being supported on said frame by means of a leaf-spring the rate of which is selected according to the desired range of frequencies of response and the physical constants of the said system.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,463,380 Harris Mar. 1, 1 4 

